Plasma etching that involves irradiating plasma on an etching film (or etching substrate) to etch the film or substrate is an indispensable process for semiconductor device manufacturing. In plasma etching, etching gas is activated by a high frequency electric field to generate plasma. Plasma includes active species such as charged particles (referred to as “ion” hereinafter) and neutral particles (referred to as “radicals” hereinafter), for example. The surface of a wafer as the etching object reacts with the ions and radicals contained in the plasma to prompt the generation of reaction products, and etching of the wafer progresses as the reaction products are volatized.
In recent years, the diameters of wafer holes are becoming larger. As the wafer hole diameter is enlarged, it becomes increasingly difficult to ensure in-plane etch rate uniformity within a wafer plane. Techniques are known for improving in-plane uniformity within a wafer plane by controlling the density of active species within a center region and an edge region of a wafer plane through adjustment of the etching gas supply rate of etching gas supplied from an upper electrode (see e.g., Patent Document 1).